Phosphorus co-doping effect on photoluminescence in Ce3+-doped SiO2 glasses: The formation of unique ligand field by P-co-doping

The origin of photoluminescence (PL) having UV emission from Ce3+ ions in P5+-co-doped SiO2 glasses was studied through the elucidation of the coordination structure around a Ce3+ by pulsed-EPR electron spin echo envelope modulatlion (ESEEM) spectroscopy. Simulation of the observed ESEEM pattern revealed that the number of P5+ in the coordination sphere is ∼10 times larger than that estimated from the random distribution of P5+, demonstrating the formation of a solvation shell structure. There are two types of the coordination manner of P–O bonds in the solvation structure, corner sharing and edge sharing. This solvation is close to that in phosphate glasses, giving a weak ligand field around Ce3+ ions, i.e., the peak position and the lifetime of Ce3+ ion move to a shorter side compared with the P-free SiO2 glass.